1. Field
The disclosure relates to communications circuitry, and, in particular, to a transformer with integrated notch filter for jammer rejection in radio receivers.
2. Background
Modern wireless devices are commonly designed to concurrently support multiple radio communications links. For example, a single smart phone device may be required to simultaneously connect to a wide-area network (WAN), a wireless local-area network (WLAN), and/or other radio-frequency (RF) communication links such as Bluetooth, etc. The presence of such multiple RF transmissions originating from the device itself, as well as from other wireless devices in its vicinity, gives rise to potentially strong jammers that can interfere with accurate reception of a desired signal by the device. Accordingly, a radio receiver must be designed to accommodate such jammers, e.g., significantly attenuate or eliminate them, in the receive signal path.
Prior art techniques for jammer rejection include providing one or more passive filters in a radio receive signal path. Such an approach undesirably increases insertion loss and correspondingly degrades the sensitivity of the receiver. Another prior art technique includes designing certain frequency-selective properties into a feedback network of a low-noise amplifier (LNA) of the radio receiver. However, such an approach may cause instability in the receiver, and also negatively impact the receiver performance.
Accordingly, it would be desirable to provide low-cost and effective techniques to provide jammer rejection for a radio receiver that do not suffer from the drawbacks of the prior art.